The present invention describes substituted sugar derivatives of indolopyrrolocarbazoles which exhibit topoisomerase-I activity and are useful in inhibiting the proliferation of tumor cells.
Topoisomerases are vital nuclear enzymes which function to resolve topological dilemmas in DNA, such as overwinding, underwinding and catenation, which normally arise during replication, transcription and perhaps other DNA processes. These enzymes allow DNA to relax by forming enzyme-bridged strand breaks that act as transient gates or pivotal points for the passage of other DNA strands. Topoisomerase-targeting drugs appear to interfere with this breakage-reunion reaction of DNA topoisomerases. In the presence of topoisomerase-active agents, an aborted reaction intermediate, termed a xe2x80x98cleavable complexxe2x80x99, accumulates and results in replication/transcription arrest, which ultimately leads to cell death. The development of topoisomerase I-active agents therefore offers a new approach to the multi-regimental arsenal of therapies currently used in the clinic for the treatment of cancer. An article in Cancer Chemother. Pharmacol [1994, 34 (suppl): S 41-S 45] discusses topoisomerase I-active compounds that are in clinical studies and these have been found to be effective clinical anti-tumor agents. Structurally these clinical candidates are related to the alkaloid camptothecin.
Indolo[2,3-a]carbazole alkaloids such as rebeccamycin (U.S. Pat. Nos. 4,487,925 and 4,552,842) and its water-soluble, clinically-active analog, 6-(2-diethylaminoethyl)rebeccamycin (U.S. Pat. No. 4,785,085), are useful antitumor agents which target DNA. Furthermore, fluoroindolocarbazoles (WO 98/07433) have been disclosed as antineoplastic agents with topoisomerase I inhibitory activity. Indolo[2,3-a]carbazole derivatives related to the Rebeccamycin class are disclosed (EP Appl. 0 545 195 B1 and 0,602,597 A2; Cancer Research 1993, 53, 490-494; ibid, 1995, 55, 1310-1315) and claimed to exhibit anti-tumor activity; however the major mechanism of action of these derivatives may not be like camptothecin, which acts as a topoisomerase I poison. Related indolocarbazoles are also disclosed (WO 95/30682) and claimed to exhibit anti-tumor activity. Hudkins, et al. have disclosed a series of fused pyrrolocarbazoles (WO 96/11933 and U.S. Pat. No. 5,475,110) and reported in vitro biological activity such as inhibition of neuronal choline acetyltransferase (ChAT) and protein kinase C (PKC) inhibition for some compounds. U.S. Pat. No. 5,468,849 discloses certain fluororebeccamycin analogs as useful antitumor agents, along with a process for their production by fluorotryptophan analog feeding of a rebeccamycin-producing strain of Saccharothrix aerocolonigenes, preferably Saccharothrix aerocolonigenes C38,383-RK2 (ATCC 39243). Glicksman, et al. disclose indolocarbazole alkaloids (U.S. Pat. No, 5,468,872), while Kojiri, et al. disclose indolopyrrolocarbazoles having a dissacharide substituent (WO 96/04293). Mazur and Hiller report the synthesis of simple 5-hydroxymethyl glycosides (J. Org. Chem. 1997, 62, 4471), while Danishefsky, et al (J. Am. Chem. Soc. 1996, 118, 2825) describe the synthesis of 5-methoxy substituted sugar derivatives. Despite these reports, there remains the need for novel and potent cytotoxic compounds useful for inhibiting topoisomerase I activity.
Thus according to a first embodiment of the first aspect of the present invention are provided compounds of Formula (I) and pharmaceutically acceptable salts and solvates thereof, useful for inhibiting topoisomerase I and the proliferation of tumor cells, 
wherein,
X1, X1xe2x80x2, X2 and X2xe2x80x2 are independently selected from the group consisting of hydrogen, halogen, cyano, OR6, xe2x80x94CF3, alkylcarbonyl, C-1-7alkyl, nitro, NR6R7, SR6 and C(O)OR6; wherein said C1-7alkyl is optionally substituted with one or more sub stituents selected from the group consisting of halogen, CN, SR6, OR6and NR6R7;
Z is selected from the group consisting of NH, O and S;
R is hydrogen, OH, OC1-7alkyl, NH2, N(C1-3alkyl)2 or C1-7alkyl, wherein said C1-7alkyl is optionally substituted with one or more substituents selected from the group consisting of halogen, CN, SR6, OR6 and NR6R7;
R1, R2, R3, and R4 are each independently selected from the group consisting of hydrogen, C1-7alkyl, C3-7cycloalkyl, halogen, azido, NR6R7, NHC(O)NR6R7, NHC(O)OR6, C(O)OR6, SR6 and OR6, wherein said C1-7alkyl is optionally substituted with one or more substituents selected from the group consisting of halogen, CN, SR6, OR6 and NR6R7; and
R5 is selected from the group consisting of C1-7alkyl, C3-7cycloalkyl, halogen, azido, NR6R7, NHC(O)NR6R7, NHC(O)OR6, C(O)OR6, SR6 and OR6, wherein said C1-7alkyl is optionally substituted with one or more substituents selected from the group consisting of halogen, CN, SR6, OR6 and NR6R7; and
R6 and R7 are independently selected from the group consisting of hydrogen, C1-7alkyl and C3-7cycloalkyl, wherein said C1-7alkyl is optionally substituted with one or more substituents selected from the group consisting of halogen, CN, OH, OC1-3alkyl, NH2 or N(C1-3alkyl)2; or
R6 and R7 together with the nitrogen atom to which they are attached form a non-aromatic 5-8 membered heterocycle containing one or two of the same or different heteroatoms selected from the group consisting of O, N and S.
According to another embodiment of the first aspect of the present invention are provided compounds of Formula (I) wherein R is hydrogen.
According to another embodiment of the first aspect of the present invention are provided compounds of Formula (I) wherein Z is NH.
According to another embodiment of the first aspect of the present invention are provided compounds of Formula (I) wherein X1, X1xe2x80x2, X2 and X2xe2x80x2 are each F.
According to another embodiment of the first aspect of the present invention are provided compounds of Formula (I) wherein X2xe2x80x2 and X2 are each F and X1 and X1xe2x80x2 are each H.
According to another embodiment of the first aspect of the present invention are provided compounds of Formula (I) wherein X2 is F and X2xe2x80x2, X1 and X1xe2x80x2 are each H.
According to another embodiment of the first aspect of the present invention are provided compounds of Formula (I) wherein X2xe2x80x2 is F and X2, X1 and X1xe2x80x2 are each H.
According to another embodiment of the first aspect of the present invention are provided compounds of Formula (I) wherein R1, R2, R3, R4 and R5 are independently selected from the group consisting of H, OH, F, azido and amino.
Other embodiments of the first aspect of the present invention provide compounds of Formula (I) comprising two or more of the above embodiments of the first aspect suitably combined.
Embodiments of a second aspect of the present invention provide a method for inhibiting tumor growth in a mammalian host which comprises the administration to said host of a tumor-growth inhibiting amount of a compound of the present invention as defined in the embodiments of the first aspect of the invention.
Embodiments of a third aspect of the present invention provide a method for inhibiting tumor growth in a mammalian host which comprises the administration to said host of a tumor-growth inhibiting amount of a pharmaceutical formulation of a compound of the present invention as defined in the embodiments of the first aspect of the invention.
Other embodiments and aspects of the invention will be apparent according to the description provided below.
The description of the invention herein should be construed in congruity with the laws and principals of chemical bonding. An embodiment or aspect which depends from another embodiment or aspect, will describe only the variables having values and provisos that differ from the embodiment or aspect from which it depends. Thus, for example, an embodiment which reads xe2x80x9cthe compound of formula (I) according to the nth aspect of the invention, wherein W is Cxe2x80x9d should be read to include all remaining variables with values defined in the nth aspect and should be read to further include all the provisos, unless otherwise indicated, pertaining to each and every variable in the nth aspect. The numbers in the subscript after the symbol xe2x80x9cCxe2x80x9d define the number of carbon atoms a particular group can contain. For example xe2x80x9cC1-7alkylxe2x80x9d means a straight or branched saturated carbon chain having from one to seven carbon atoms, including without limitation groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, t-butyl, n-pentyl, sec-pentyl, isopentyl, n-hexyl and n-heptyl. The term xe2x80x9chalogenxe2x80x9d includes fluoro, chloro, bromo and iodo.
It is to be understood that the present invention includes any and all possible stereoisomers, geometric isomers, diastereoisomers, enantiomers, conformational isomers and anomers, unless a particular description specifies otherwise.
The numbers in the subscript after the symbol xe2x80x9cCxe2x80x9d define the number of carbon atoms a particular group can contain. For example xe2x80x9cC1-6alkylxe2x80x9d means a straight or branched saturated carbon chain having from one to seven carbon atoms including without limitation groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, t-butyl, n-pentyl, sec-pentyl, isopentyl, n-hexyl and n-heptyl. xe2x80x9cArylxe2x80x9d means an aromatic hydrocarbon having from six to ten carbon atoms; examples include phenyl and naphthyl. xe2x80x9cSubstituted arylxe2x80x9d or xe2x80x9csubstituted aralkylxe2x80x9d means an aryl or aralkyl group independently substituted with one to five (but particularly one to three) groups selected from the group consisting of C1-6alkanoyloxy, hydroxy, halogen, C1-6 alkyl, trifluoromethyl, C1-6alkoxy, C2-6alkenyl, C1-6alkanoyl, nitro, amino, cyano, azido, C1-6 alkylamino and amido. The term xe2x80x9chalogenxe2x80x9d includes fluoro, chloro, bromo and iodo.
The compounds of this invention can exist in the form of pharmaceutically acceptable salts. Such salts include addition salts with inorganic acids such as, for example, hydrochloric acid and sulfuric acid, and with organic acids such as, for example, acetic acid, citric acid, methanesulfonic acid, toluenesulfonic acid, tartaric acid and maleic acid. Further, in case the compounds of this invention contain an acidic group, the acidic group can exist in the form of alkali metal salts such as, for example, a potassium salt and a sodium salt; alkaline earth metal salts such as, for example, a magnesium salt and a calcium salt; and salts with organic bases such as a triethylammonium salt and an arginine salt. The compounds of the present invention may be hydrated or non-hydrated.
The compounds of this invention can be administered in such oral dosage forms as tablets, capsules (each of which includes sustained release or timed release formulations), pills, powders, granules, elixirs, tinctures, suspensions, syrups and emulsions. The compounds of this invention may also be administered intravenously, intraperitoneally, subcutaneously, or intramuscularly, all using dosage forms well known to those skilled in the pharmaceutical arts. The compounds can be administered alone but generally will be administered with a pharmaceutical carrier selected on the basis of the chosen route of administration and standard pharmaceutical practice. Compounds of this invention can also be administered in intranasal form by topical use of suitable intranasal vehicles, or by transdermal routes, using transdermal skin patches. When compounds of this invention are administered transdermally the dosage will be continuous throughout the dosage regimen.
One aspect of the present invention involves administration of the compounds of the present invention, or pharmaceutically acceptable salts or solvates thereof, to a mammal implanted with a tumor or susceptible to cancer formation. In general the compound would be given in a dose range of from about 0.1 mg/kg to about the MTD (maximum tolerated dose). The dosage and dosage regimen and scheduling of a compound of the present invention must in each case be carefully adjusted, utilizing sound professional judgment and considering the age, weight and condition of the recipient, the route of administration and the nature and extent of the cancer disease condition. The term xe2x80x9csystemic administrationxe2x80x9d as used herein refers to oral sublingual, buccal, transnasal, transdermal, rectal, intramascular, intravenous, intraventricular, intrathecal, and subcutaneous routes. In accordance with good clinical practice, it is preferred to administer the instant compounds at a concentration level which will produce effective beneficial effects without causing any harmful or untoward side effects.
Procedures for the preparation of compounds of Formula (I) are illustrated in Schemes 1-5 and the preparation of the key intermediates/starting materials is illustrated in Scheme 6. 
In Scheme 1, the mono- or dianion of 1 was generated using a suitable base, such as sodium hexamethyldisilazide, and was glycosylated with a chlorosugar derivative like 2 to give a protected glycoside (3). Deprotection of the imide moiety was done by base-induced hydrolysis, followed by acidification to give an intermediate anhydride. The latter was conveniently converted to an imide using a suitable amine, such as that provided by reaction with a mixture of hexamethyldisilazane and methanol in dimethylformamide (cf. P. D Davis, R. A. Bit Tetrahedron Lett. 1990, 31, 5201). Selectively deprotected glycosides like 5 and 12 could then be prepared by treatment of the corresponding perbenzylated glycosides with zinc chloride in acetic acid-acetic anhydride (cf F. Kong, et al. Tetrahedron Lett. 1997, 38, 6725) or with iodine in acetic anhydride (cf K. P. R. Kartha, R. A. Field Tetrahedron 1997, 53, 11753), followed by hydrolysis of the intermediate acetates. The resulting primary alcohols could be oxidized under mild conditions, for example using Dess-Martin periodinane or the like, to give the corresponding aldehyde. These aldehydes readily underwent xcex1-hydroxymethylation followed by spontaneous Canizzaro reduction in the presence of aqueous formaldehyde and aqueous sodium hydroxide (cf A. W. Mazur, G. D. Hiler J. Org. Chem. 1997, 62, 4471) to give 5xe2x80x2-C-hydroxymethylglycosides such as 7. If during the course of this reaction the imide moiety was hydrolyzed to the corresponding anhydride, this was readily converted back to an imide by treatment with a suitable source of ammonia, such as ammonium acetate. Finally, removal of the benzyl protecting groups was then done using a conventional procedure involving hydrogenolysis over Pearlman""s catalyst (20% Pd(OH)2 on charcoal), to give a deprotected glycoside (8).
As shown in Scheme 2, the 6xe2x80x2-hydroxyl group of 5 may also be activated, for example as its mesylate and subsequently as the corresponding iodide (9), which may then undergo elimination of the element of HI using a suitable amine base, such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), to give a vinyl ether (10). Subsequent removal of the benzyl protecting groups using boron tribromide, followed by quenching of the reaction mixture with methanol, affords a 5xe2x80x2-C-methoxyglycoside such as 11. Alternatively, as shown for example in Scheme 3, introduction of a 5xe2x80x2-C-methoxy group could precede the final deprotection step. Thus, a vinyl ether (13) can be epoxidized under mild conditions using dimethyldioxirane in acetone (cf S. J. Danishefsky, et al. J. Am. Chem. Soc. 1996, 118, 2825), and the resulting epoxide (14) can undergo solvolysis with methanol in the presence of zinc chloride and final deprotection as before to give a 5xe2x80x2-C-methoxyglucoside (15).
Selected examples of 5xe2x80x2-C-methoxyglycosides could also be prepared as shown in Scheme 4. Thus, treatment of a selectively deprotected galactoside (16) with the well-known fluorinating agent DAST [(diethylamino)sulfur trifluoride], followed by debenzylation as before, takes an unexpected course to give predominantly the 5xe2x80x2-C-methoxyglycoside 17.
Alternatively, as shown in Scheme 5, a vinyl ether (18) may be treated with an alcohol, for example methanol, in the presence of a small amount of an acid catalyst, such as p-toluenesulfonic acid, to give a protected 5xe2x80x2-C-alkoxyglycoside. The latter was deprotected as before to give a 5xe2x80x2-C-alkoxyglycoside (e.g., 19).
A key intermediate sugar was prepared as shown in Scheme 6. Conversion of a commercially available methyl-xcex1-D-glucopyranoside (20) to a 4-deoxyglycoside (22) was done as reported by Barrette and Goodman (J. Org. Chem. 1984, 49, 176). Deprotection of the anomeric position could be done in two steps, first by treatment with benzenethiol and a Lewis acid, such as boron trifluoride etherate (cf L. A. Paquette, J. A. Oplinger J. Org. Chem. 1988, 53, 2953), followed by hydrolysis of the resulting phenylthio sugar derivative (23) using N-bromosuccinimide in a suitable solvent, such as acetone or acetonitrile, in the presence of water (cf B. Fraser-Reid, et al. J. Am. Chem. Soc. 1988, 110, 2662). Alternatively, deprotection of the anomeric position could be effected in one step by treatment with a suitable acid, such as 90% formic acid, to give the glucopyranoside (24) directly. Conversion of a glycopyranoside, such as 24, to a glycopyranosyl chloride (2) could be done according to a procedure reported by Iversen and Bundle (Carb. Res. 1982, 103, 29).
The compounds which constitute this invention and their methods of preparation will appear more fully from a consideration of the following examples which are given for the purpose of illustration only and are not to be construed as in any way limiting the scope of the invention.
Several intermediate compounds, as well as other conventional starting materials (e.g., 20), used in the preparation of compounds of Formula (I) were generally commercially available. Representative syntheses of some of these compounds are provided hereinbelow nevertheless.
All anhydrous reactions were performed under an atmosphere of nitrogen or argon using either commercially available dry solvents or freshly distilled solvents. Melting points were determined in an open capillary tube with a Thomas-Hoover melting point apparatus and are uncorrected. Column chromatography was performed using EM Science silica gel 60 (230-400 mesh) with the designated solvent system as eluant. Thin-layer chromatography was done on E. Merck silica gel 60 F254 plates (0.5 mm). Hplc purity determinations were done using either a Shimadzu LC-10AS with a SPD-10AV UV-V is detector and one of the following columns; YMC Combiscreen ODS-A (4.6xc3x9750 mm), or HP Zorbax SB-C18 (4.6xc3x97750 mm); or, an HP 1090 DR5 with a diode array detector and a Waters Nova-Pak C18 column (3.9xc3x97150 mm). Infrared spectra were recorded on a Nicolet Protxc3xa9gxc3xa9 460 FTIR as thin films or KBr pellets. 1HNMR spectra were recorded on either a Bruker AMX-400 or a Bruker ARX-500 NMR spectrometer and chemical shifts are expressed in parts per million (ppm or xcex4) with the solvent in use as internal standard. Coupling constants are given in hertz and multiplets are designated as follows; singlet (s), doublet (d), triplet (t), quartet (q), muliplet (m), and broad (br). Low resolution mass spectra were determined on a Finnigan Matt TSQ-7000 triple stage quadrapole spectrometer (positive/negative ESI) operated in the negative ion mode.